August 1, 2006. The peregrines at the Precipice are pretty active lately! With the Precipice and East Face trails opening last Friday, they are still getting accustomed to “intruders” in their home, which may explain their greater visibility recently. They aren’t attacking any unwary hikers, but visitors have reported seeing them dive and chase each other near to them while they were hiking the trail! The adults have been seen more often lately as well, and their presence results in quite a ruckus from the juveniles, who start squawking and chasing after them!
Some visitors and staff witnessed an exciting display on Saturday when one juvenile chased another one from the meadow back to the cliff. The pair swooped over us, a mere 10 feet above our heads! You never can tell what these peregrines will do. As the nesting season winds down, rangers will eventually no longer be observing the falcons at the Precipice. There will still be opportunities to see peregrines in the park, so keep your eyes peeled. Juveniles from both the Precipice and Beech Cliffs could be seen soaring around anywhere as they become more independent. The adults of all four pairs are still here as well, and they will not migrate south until the fall.
Well, this will be the last edition of View from the Aerie this season. As mentioned, the Precipice and East Face trails are now open. Beech Cliffs remains closed, along with Flying Mountain, and the north section of the Flying Mountain Trail is still closed to hiking. Rangers will continue to staff the Precipice trailhead parking lot for at least the remainder of the week. Then be sure to join us in a few weeks on top of Cadillac Mountain for Hawkwatch 2006. Hawkwatch is an exciting program that will begin on Tuesday, August 22. Come help collect data on all sorts of migrating raptor species, including peregrine falcons!
July 25, 2006. We are closing in on the time when the juveniles at the Precipice will have dispersed for good. The timing of dispersal varies from site to site and even among individuals, but at this location has tended to be around 5-6 weeks after the young have started flying. Dispersal is prompted by a number of factors. The juveniles may be driven off by their parents, or their parents may simply refuse to continue feeding them, forcing the juveniles to go off in search of food. Also, the juveniles might just start hunting on their own and seek out a site with less competition from family members. Males not only develop faster and tend to start flying before their sisters, but also they often disperse at a slightly younger age; therefore it is likely that the single male juvenile will leave the area before his three sisters. Nevertheless, we have still recently seen all four juveniles around the Precipice, and it is likely that at least some of them will be in the area for at least a couple of weeks longer.
We are lucky to have four pairs of peregrine falcons here in Acadia National Park, considering there are currently only a total of 19 pairs in the entire state of Maine. This year, of those 19 pairs, only 11 actually attempted to nest, and nine of those pairs were able to produce young. There were about 22 peregrine chicks hatched in the state this year, and seven of those were from Acadia! The success of our peregrines is probably due in part to the extra protection we can give them as a national park. Just by monitoring them regularly and closing some of the trails near the nesting site, we can limit the amount of human disturbance that could affect the birds and their nesting success.
Even with the juveniles nearly independent, it is still important to regulate the amount of disturbance near their nesting cliff. Climbing on the cliff and hiking near the aerie can agitate the peregrines, so state biologists recommend maintaining trail and cliff closures during the peregrine falcon nesting season between March 15 and August 15. Furthermore, because peregrines are territorial and aggressive, they often do not hesitate to dive at and attack humans if they feel threatened by them. Thus, trail closures are an important management tool to protect these endangered birds, as well as to protect unwary hikers!
Acadia National Park cooperates with state biologists to help encourage the recovery of the peregrine falcon here in Maine. There are also many things private landowners can do to help the success of these magnificent birds. The Maine Department of Inland Fisheries and Wildlife (MDIFW) recommends consulting with a MDIFW biologist before commencing land development near a known aerie. Also, it is important to protect wetlands from filling and development because they are important habitat for many species, including some prey species of peregrines. Additionally, keeping large trees and dead snags is great for peregrines, because they use those perches to roost and scout for food. With continued cooperation between state and federal agencies, individuals, and landowners, we can help ensure the continued success of peregrines here in Maine well into the future.
The Precipice and East Face trails are still currently closed, along with the north section of the Flying Mountain trail. But the juvenile peregrines won’t be here for much longer, so if you have yet to see them, be sure to drop in at the Precipice between 9a.m. and 12 p.m. (weather permitting) to see if you can find them!
July 18, 2006. Well, it is hit or miss these days as far as peregrine watching goes. At the Precipice, the juvenile peregrine falcons have been on the wing for between four and five weeks now. Within the next couple of weeks the juveniles will continue to range farther from the cliff until eventually we will no longer see them at all. Sometime in September the young will begin their migration south for the winter. It is difficult to say where in particular our birds go for the winter months. However, one peregrine that was banded at Jordan Cliffs in 1997 was unfortunately shot in Cuba that following winter. Therefore, we can surmise that peregrines from Acadia can and do migrate at least as far as Central America and the Caribbean.
The adults will migrate as well; however, peregrines tend not to travel as a family group. Also, these particular adults at the Precipice may actually be non-migratory. Observers have occasionally seen adult peregrines around Champlain Mountain at various times during the winter. As long as there is enough food to eat, it is unnecessary for the falcons to expend all of that energy to migrate hundreds of miles. Plus, if the adults stick around they can be sure to keep their “home” at the Precipice. That cliff site is ideally located to great habitat for their prey, being near a large meadow and wetland, as well as being close to the sea. Also, there is fresh water for drinking and bathing at Beaver Pond and in smaller wetlands in the meadow below the cliff. In fact, it is such a great territory, that it is the only site in the park where peregrines have been successful in raising chicks every year since 1991. Other peregrines would recognize it as an ideal territory as well, so by staying through the winter the Precipice pair can better defend their cliff from other competitors.
Whether or not the adults remain through the winter or return each spring, the young juveniles will not return to the Precipice next year. Peregrines are so territorial that their parents would chase them off. If the youngsters survive the winter and two migrations, they will wander until they find their own territory. We have received reports of our peregrines nesting in a variety of locations in the northeast. Although only one of the hacked peregrines released on Jordan Cliffs between 1984 and 1986 returned to nest in Acadia, one female released in 1986 was seen nesting in 1997 in New York City, and another female also released in 1986 was seen alive in 1989 on Long Island. Of the naturally hatched chicks, a female banded in 1994 at the Precipice was seen nesting in Boston in 1996 and 1997, while her sister was seen nesting in New Hampshire between 1997 and 2000. Another female banded at the Precipice in 1997 was seen in Maryland in 1998, a female hatched on Jordan cliffs in 1999 was found this year with a broken wing in Washington, DC, and a 2000 female from Jordan cliffs was recorded successfully nesting in Vermont, with three chicks in 2004, and another one in 2005.
What stimulates peregrines to disperse and migrate? It is not clearly understood. The young may venture off on their own, or the adults may eventually chase them away. As to migration, peregrines from different latitudes migrate different distances, with birds from the furthest north tending to migrate the furthest south. The migration of their prey species may influence the timing of the peregrine’s migration. Photoperiod and genetic control have also been suggested as alternative explanations. Whatever the case, be sure to stop in at the Precipice between 9 a.m. and 12 p.m. (weather permitting) to see the peregrines before they leave!
July 11, 2006. This year’s peregrine chicks are developing on schedule, under the watchful eyes of park staff and curious visitors. The young at Beech Cliffs, being a few weeks younger than the juveniles at the Precipice, are a few weeks behind them in their development. They haven’t started hunting for themselves yet, but are “killing” sticks or other inanimate objects, pursuing insects, and practicing flight maneuvers. The three young fledged a couple of weeks ago, although one unlucky youngster learned the hard way…A park employee was observing the peregrines at that location when one of the juveniles hopped onto a flimsy branch above the nest site. The branch was unable to support the falcon’s weight, and the juvenile tried to hang on, even upside down, as the branch bent over. It had a rough tumble, but appeared to put its wings out just before it disappeared out of sight. After many hours of observation in the past two weeks, we have finally been able to ascertain that all three juveniles are fine!
Meanwhile, we are starting to see less and less of the young peregrines at the Precipice, and soon we won’t see them at all. As the youngsters get closer to dispersing, they range farther and farther from the cliff site. On one occasion last week we only observed a couple of the juveniles for about ten minutes in the entire three hours, and on Monday, the young were only around for about an hour. For part of that time they were seen circling over the meadow below the cliff, probably playing with each other in the wind and hunting for a snack!
It is interesting to note that although the falcons pluck some of the feathers of their prey before devouring it, it would be a highly time-consuming process to pick all of those feathers out and then pick the meat bits off the tiny bones. Therefore, like owls, peregrines and many other raptors regurgitate pellets of indigestible material, such as bones and feathers. Peregrines also leave the inedible wings of their prey all around the cliff. While we have been seeing less of the peregrines lately, we have been seeing more turkey vultures circling near the cliff. The adult peregrines aren’t chasing them off anymore, and the young lately either haven’t been around or haven’t been bothered by their presence. The vultures are probably taking advantage of the thermals and wind currents that rise up over the cliff. They may also be looking for a meal from the inedible bird parts left around the cliff, as well as food cached by the peregrine falcons to eat later. Also, if the young accidentally drop food in flight (such as when they are harassed by their siblings trying to steal an easy meal), they tend not to recover prey from the ground. Thus, if there are any prey remains decaying up on that cliff, the turkey vultures can smell it!
Be sure to stop in at the Precipice any day between 9 a.m. and 12 p.m. (weather permitting) and see if you can catch some of the final glimpses of the young this year!
July 4, 2006. Ever since the peregrine young at the Precipice fledged, they have been establishing the skills they will need to survive on their own. It is a rough life out there in the “real world,” and most juveniles do not survive the first year. Not only do they need to be able to identify appropriate food and become successful hunters, but they also must learn how to defend themselves and avoid predation, and they need to be skilled fliers before dispersing and migrating. As they get older, the juveniles will need to know how to compete with other peregrine falcons for a nesting territory or mate, and how to deter potential predators from their nest.
At this stage the young are beginning to exhibit defensive behaviors when an unfamiliar individual approaches the cliff too closely. Sometimes the young will only object vocally at the presence of other large birds or lazily follow them away from the cliff. But when the juveniles exhibit more intense aggression, they may pursue the intruder in a high-speed chase and dive-bomb the offending bird, occasionally striking it with its talons. A couple of weeks ago observers witnessed the adult female and two of her young attacking a juvenile bald eagle, and on another occasion the young went after a turkey vulture!
Other exciting behaviors that we have witnessed at the Precipice include the juveniles chasing and diving at each other, as well as trying to grapple with each other in the air with their talons. Just as human babies learn by playing, as the juveniles interact with each other they are developing and refining skills like defending themselves from predators or competitors. The juveniles are also competing amongst themselves for food, and have been ever since they were hatched. Thus, by being coordinated enough to flip upside down and precisely lock talons, the juveniles could potentially steal prey items from each other in flight. This sibling rivalry is a survival mechanism: if there were a lack of food, a stronger juvenile would be able to ensure its own survival at the expense of its weaker sibling. However, when the adults are experienced at raising young and successful hunters, there is usually enough food to go around. Experienced adults will try to make sure that all the young are fed enough to ensure their survival until dispersal. Being able to interlock talons in flight is a skill also observed in adults. When the young mature and find a mate, the males will bring food to the females throughout the breeding season. An aerial food transfer, from one bird’s talons to the other’s while in flight, is a common method of achieving this exchange.
Recently at the Precipice we have often only been able to observe the juveniles. They have been more active lately than the adults and are therefore easier to find. However, the adults also tend to be more secretive now. As the juveniles get older, they become more and more antagonistic toward the adults, soliciting food aggressively. The adults try to stay out of their view to avoid being attacked, unless they are bringing in food for the young. Almost every time the adults appear, the juveniles will chase them regardless of whether they have food or not. Nevertheless, the adults are still much faster flyers and can escape the young in flight if necessary.
These are common patterns of behavior in juvenile peregrines worldwide and a natural part of their development. So be sure to stop in at the Precipice between 9 a.m. and 12 p.m. (weather permitting) to see their continuing progress before they take off for good!
June 27, 2006. It is often difficult to locate the peregrines on a cliff face. Between the sheer size of the cliff and how well their plumage blends with the rock and lichen, they become practically invisible. Often the only way we are able to find them is to see them in flight and watch closely where they land. However, if we are able to locate one of the birds and they stay in that spot for a while, we not only get to see great views of them with the spotting scopes, but also gain an appreciation of their perching behavior. Peregrines of all ages exhibit a wide repertoire of behavior while perched.
One day a visitor watched a perched juvenile intensely watching a butterfly as it zoomed past. Young falcons are often seen craning or inverting their heads in curiosity as they examine the new world beyond the nest site. Curiosity toward flying insects may be related to their innate desire to hunt flying prey. A few days ago we also witnessed two of the juveniles perched together and seemingly nibbling at each other’s heads. Actually, the birds were pulling each other’s feathers through their beaks to clean and straighten them. Preening is a necessary and frequent activity in which an individual realigns its feathers and removes dirt and parasites. Peregrines often perform this grooming activity on themselves, but juveniles may mutually preen each other; it is also seen between adults during courtship. It is impossible for a bird to preen its own head with its beak, so this is often accomplished with the help of another bird, or else the individual will rub its head with its wing or scratch it with its talon.
Soliciting food is another behavior that we have often witnessed. The juveniles have relied upon their parents to feed them for their entire lives, and will continue to do so for a little longer until they begin to hunt and are efficient at it. Hence, the juveniles tend to primarily associate the adults with food and will often beg and harass the adults whenever possible in the hopes of obtaining another meal. They frequently solicit food by vocalizing loudly from their perch, and if an adult is in view they may give chase. A little over a week ago we watched the juvenile male calling and chasing the adult female. She had a relatively large bird in her talons, which she dropped in mid-air for the juvenile. He did not retrieve it, and within seconds the adult female had swooped down and recovered the falling prey. The exciting chase continued until the juvenile was finally able to grab the prey from the female’s talons! Soon the juveniles will progress to “aerial live-drops” where the adults will capture a bird but not kill it. They will carry it in their talons and encourage the young to chase them until the adult releases the bird, and it is up to one of the juveniles to capture and kill the fleeing prey. By feeding the young in this way, the adults are in essence training them to hunt for themselves.
In other peregrine news, it seems that the pair at Jordan Cliffs has definitely failed. We are uncertain why this pair has been unsuccessful, but we hope that future tests on an egg retrieved from the nest site by park staff will provide some clues. Due to the failure, the Jordan Cliffs Trail has just been reopened (the Precipice, East Face, and north section of Flying Mountain trails remain closed). The three young at Beech Cliffs are almost 40 days old now and should be fledging soon. The pair at Valley Cove remains mysterious, and we are still uncertain of their productivity.
If the weather allows, join us at the Precipice every morning between 9 a.m. and 12 p.m. to observe the exciting behaviors of these peregrines!
June 20, 2006. The chicks at the Precipice have finally taken to the skies! They are not, however, quite as skilled at flying as their acrobatic parents yet. The young will stick around the cliff area for another five weeks or so while they practice flying, landing, chasing, and hunting. It is a very exciting time to observe these magnificent birds, so join us each day at the Precipice (weather permitting!) between 9 a.m. and 12 p.m. to see how they are doing!
It was not always possible to observe peregrine falcons at the Precipice. Although DDT prevented the death of many people due to malaria and other insect-born diseases, it greatly affected the reproductive capabilities of peregrine falcons and other raptors, eventually wiping out the population of these species in many areas. The use of DDT was banned in most European and North American countries in the early 1970s, and populations are rebounding. But this is not the end of the story. DDT is still produced today. It is used in other countries, primarily in South America and Africa. Many bird species, including peregrines and a lot of their prey species, migrate to these areas in winter and continue to build up DDT in their systems. Additionally, DDT persists in the soil and marine sediments in other countries even today. DDT is found in the egg shells of bald eagles here in Maine and continues to affect the other top avian predators in our state.
Although peregrines were extirpated from this area by the early 1960s, we are lucky to again have peregrines here in Maine and throughout the eastern U.S. This was accomplished by an extensive reintroduction program. Falconers were instrumental in the recovery of peregrines. They provided much-needed knowledge, such as how to raise falcons in captivity and how to find wild nests. Furthermore, they had developed a process called hacking, which they used to condition their young falcons. Hacking was adapted for peregrine reintroductions. Peregrine falcons were bred in captivity from artificial insemination of adult falcons taken from other subspecies and from falconers’ collections. Genetically-speaking, because there were so few peregrines of the eastern subspecies left, the falcons released to the wild were a mixture of subspecies from around the world. These chicks were placed in hack boxes on cliffs, and food was delivered to the box via a tube so that the young would not associate humans with food. These boxes protected them from predators until they were about 40 days old and had all of their flight feathers, at which point the boxes were opened. Usually within days the young would begin flying and attempting to hunt. It was hoped that the chicks that survived to the following year would eventually return with a mate to the cliff where they were hacked and begin to breed.
Here in Acadia National Park, chicks were hacked at Jordan Cliffs between 1984 and 1986, with 22 chicks released into the wild. In the spring of 1987, a peregrine that was hacked the previous year was observed sitting on the hack box. No hacked chicks were released that year since a mature peregrine would not tolerate other youngsters in their territory. This peregrine was observed near Champlain Mountain each year through 1990, and finally in 1991, he found a mature mate. They successfully fledged three young from the Precipice site. Peregrines have been successfully nesting there ever since. In 1995, one of the young that had been banded and fledged from the Precipice the previous year took up residence at Beech Cliffs, where she mated and raised one chick. The year 1997 marked the first successful nesting at Jordan Cliffs, and a pair first attempted nesting at Valley Cove (Eagle Cliffs) in 1999. Since 1991, 77 chicks have fledged from Acadia National Park. Actually, make that 81, including the young at the Precipice this year!
June 13, 2006. How did peregrine falcons become endangered in the state of Maine? There are few historical records of peregrine falcon populations in Maine; however, sixteen aeries were documented in the state. This number probably underestimates the population that was here. Two of those historical aeries were here in Acadia National Park: one on Champlain Mountain (the Precipice) and the other on St. Sauveur Mountain (Eagle Cliffs). Peregrines were last nesting here in Acadia at the Precipice in 1956. In 1965, the last peregrine was seen and documented in the park at Eagle Cliffs searching for a mate.
The subspecies of peregrine falcon east of the Mississippi River was extinct by the mid-1960s. Furthermore, the plight of the peregrine was not local, but worldwide, and other raptors were suddenly suffering from diminishing populations as well. Peregrines were often killed by farmers, thinking they posed a threat to their poultry, and were shot during World War II to prevent them from preying on the homing pigeons that were being used as messengers. Eggs were collected as a hobby, and chicks were taken from the aeries to be used by falconers. And while these factors had local effects on peregrine populations, they did not cause the widespread destruction and extinction of an entire subspecies of peregrines. Rather, a chemical called DDT was the culprit.
DDT was developed in 1939 and used extensively during and immediately after WWII as a pesticide. It is extremely successful at rapidly killing aphids, flies, mosquitoes, and some other pesky insects. Perhaps more importantly, it effectively killed those insect species that can carry diseases that pose a threat to humans, such as malaria-carrying mosquitoes and the lice that carry typhus. Because DDT was not harmful to humans, it was sprayed in many places on the landscape, and the World Heath Organization estimates that 25 million people were saved from these insect-spread diseases because of the widespread use of DDT. However, for the peregrine and other raptor populations, the use of DDT was not beneficial.
DDT is a persistent chemical, meaning it does not break down rapidly, even when ingested. As it was sprayed on the land, it (and its breakdown product DDE, which is also highly persistent), entered the soil and was absorbed by some species such as earthworms. DDT was also washed into rivers and the sea in runoff, where it is highly toxic to many invertebrate and fish species. These species would be consumed by other animals such as robins and seabirds, which in turn may become prey for raptors like the peregrine falcon. To survive, one robin would need to eat many earthworms, and one peregrine would need to eat many robins to meet their energy needs. DDT would accumulate in organisms at each step in this food chain, and became concentrated in top predators such as peregrines. This bioaccumulation affected their reproductive systems, resulting in thin eggshells that would break when the female settled on them to incubate. Years went by and no young were being produced to replenish the population, resulting in the worldwide decline of the peregrine falcon.
Next week I will let you know how peregrine falcons once again grace the skies in Acadia, so stay tuned! We are still on the edge of our seats waiting for three of the chicks at the Precipice to start to fly (one started Monday), so be sure to come see the peregrines in action for yourself between 9 a.m. and 12 p.m., weather permitting.
- Lindsey Fenderson
June 6, 2006. The chicks at the Precipice are getting more of their juvenile feathers in every day. They are stretching and exercising their wings in preparation for that first flight. They are also eager to start exploring their world; sometimes we see one of the chicks sitting out on the ledges outside of the aerie. Peregrines usually fledge between 4.5 and 6 weeks of age, so we expect to see these youngsters in the air in another week!
The peregrine falcons on Beech Cliffs were successful again this year. Last year, three chicks fledged from that site and observers have seen at least two chicks in the nest this year. We are not yet certain of the status of the pairs on Jordan Cliffs and Flying Mountain. We have repeatedly observed an adult peregrine sitting on the nest site at Jordan Cliffs; however, it is late in the season for her to have eggs. Young hatchlings may be brooded until they are almost two weeks of age, but we have not observed any chicks or food being brought to the nest. Adults have been seen going in and out of the nest site at Valley Cove, although we have not been able to confirm their status. The pair at Valley Cove was not successful last year, and the Jordan Cliffs site has not been successful in the prior two years. Nests may fail for a number of reasons, including weather, experience of the adults, disturbance, food availability, toxin accumulation, and predation.
Weather is a major factor. For instance, May 2005 was extremely rainy, and peregrine falcon pairs across the state had little success in raising young. Also, spring storms may sweep eggs or young chicks off the cliff.
Successful nesting also depends on how experienced the adults are at caring and providing for their chicks. More experienced adults can produce and care for larger broods, may be more experienced hunters and defenders of the nest, and may make better choices when choosing a nest site.
Human disturbance negatively affects the success of a nesting pair. If the adults are too busy defending the nest, they can’t hunt for themselves or the chicks, or may be too occupied with diving at humans to prevent another opportunistic predator from accessing the young. Eggs and young chicks are also extremely susceptible to poor weather. If an adult (usually the female) is disturbed from the nest and hence unable to provide heat for the eggs or young when it is cold, rainy, or snowing, they may perish. “Siblicide” may also occur; when there is not enough food to go around, the older, stronger chicks may kill their weaker sibling to help ensure their own survival.
Toxins and pesticides in the environment are incorporated in the food web and accumulate in these falcons. Across the world these poisons continue to affect the reproductive capability, egg structure, fertility, and the general health of the peregrine population.
Peregrine chicks or eggs may also be taken by predation. Most peregrines nest on steep cliff faces or skyscrapers, which are generally inaccessible to mammalian predators, such as raccoons or foxes. However, other raptors wouldn’t hesitate to take a peregrine chick. The biggest threat to peregrine young in this area (besides humans) is probably the great-horned owl. Falcons have superb sight during the daytime, but are at a distinct disadvantage when compared to owls at night.
Be sure to stop in at the Precipice this week between 9 a.m. and 12 p.m. (weather permitting) and see if you can catch the young peregrines taking some of their first flights!
- Lindsey Fenderson
May 30, 2006. We have four healthy chicks at the Precipice this year! It was certainly an exciting week—for the first time since 2000, it was possible to band the Precipice chicks. This was not feasible in recent years for a variety of reasons. There is a very small window of time when peregrine chicks can be banded, usually when the chicks are about 21 days old. The chicks must be large enough that their legs are nearly full grown so the bands fit properly. However, if the chicks are too old, they are more aggressive and may try to jump off the cliff to escape before they have their flight feathers and thus are unable to fly. By monitoring the nest site and the adults’ behavior we can usually judge when the eggs hatched and thus when the chicks are roughly three weeks old. Additionally, a federally-licensed bander as well as a rock climber must be available at that precise time period, and the weather must cooperate so that is safe to go up the cliff.
It was quite a process to band the chicks. Because the aerie is located on a cliff face, a skilled rock climber is needed to get to the chicks. Dave Smith, part of the Resource and Visitor Protection Division of Acadia National Park, was just such a person. Onlookers watched all morning as he made his way up the Precipice Trail and eventually belayed down to the nest. The adult peregrines were not at all pleased with the intrusion. They dived vigorously at Dave and vocalized repeatedly in an attempt to protect their young. Luckily, the adults didn’t get close enough to actually harm him!
Once at the nest, Dave placed the chicks in a bag and lowered them safely to the trail below using a rope. Waiting to catch them were Bruce Connery, Acadia National Park biologist, and Charlie Todd, Maine Department of Inland Fisheries and Wildlife biologist. The chicks were fitted with a silver U.S. Fish and Wildlife Service band on their left leg and a bi-colored band (black over green) on their right. The colored bands are easier to see from a distance, and the color combinations tell us where the bird was banded. Black over green bands indicate that the falcons were banded in the state of Maine. Judging from the amount of juvenile feathers that had grown in on the chicks, they ranged in age from 21 to 25 days old as of Thursday, May 25. Eggs are not laid all at once; there is often an interval of about a day between each egg. Therefore, the chicks do not hatch at exactly the same time and are slightly different ages.
Valuable information is obtained from bird banding. Because females are larger, they need slightly larger leg bands. Based on leg size, the biologists determined that three of the chicks were female, and one was male. A few feathers were taken from one of the chicks, which will be tested for metals and contaminants. Top predators like falcons are greatly affected by environmental contaminants such as pesticides, so testing their feathers will help give biologists an idea of how much they are consuming. Also, if we are able to recover the bands, either in hand from a dead bird or by visually observing a live bird, we can gain valuable information about migration routes, juvenile dispersal, and survivorship.
Once banded, the chicks were raised back up the cliff face and returned to the nest. Most birds have a very poor sense of smell and so the limited handling of the chicks by the biologists did not affect how the adult peregrines respond to their young. The adult peregrines returned to the nest only fifteen minutes after the park staff left the cliff. The entire process took around six hours. During this time, because the adults were so busy trying to defend the nest and their young, they did not spend any time hunting or feeding the chicks. This is precisely why park trails near peregrine falcon nests remain closed until the chicks are no longer using the area. Continuous human disturbance would cause these nests to fail. Although the peregrine falcon is no longer considered endangered nationally, they are still endangered in the state of Maine, with less than 30 breeding adults in the entire state. Thus, to help protect part of Maine’s small peregrine population, the Precipice, East Face, Jordan Cliffs, and the north section of Flying Mountain Trails will remain closed until the young peregrines leave their respective cliffs.
The Precipice trailhead is staffed every day from 9 a.m. to noon, weather permitting, so come see how the young are doing!
- Lindsey Fenderson
May 23, 2006. Welcome to this year’s first edition of View from the Aerie! My name is Lindsey Fenderson, and I am this season’s raptor intern. I recently graduated from the University of Maine, Orono, with a B.S. degree in Wildlife Ecology, and will be reporting weekly on what is going on with our peregrine falcons in Acadia National Park.
We are lucky to again have four breeding pairs of peregrines here in the park. Although they may not all be able to successfully produce young, the pair at the Precipice has at least two chicks! We have been watching the behavior of the adults closely and believe the chicks at the Precipice hatched around May 3. Both adults appear to be the same individuals that were at this site last year, which would make this possibly the fourth year at the Precipice for this female, and the second year for the male.
Peregrine falcons are monogamous and mate for life, although they may be more attached to the nesting territory than each other. Each fall once the young have dispersed, migratory peregrine couples typically part ways and head south for the winter. The following spring they return to take up residence at their breeding territory. If their mate does not return to the site around the same time, they will find a new mate. Resident pairs also generally remain attached to their territory and each other for life. Whether migratory or not, this is not to say that “divorce” does not occur when the nest is unsuccessful, and females have been recorded changing sites.
Pairs do not always establish their aerie (the nest of a bird of prey) in precisely the same location from year to year, but they may use a site more than once. Interestingly, when new pairs “move in” to a territory, they are often seen using traditional scrapes (nest sites) that were used by previous residents in the past. This has occurred at the Precipice, where the adults on this cliff are using the old raven’s nest, a popular site that has been used by nesting peregrines in seven other years since 1991.
We have seen some very exciting behavior at the Precipice so far. The adult male often brings in food, and when the female sees him she sometimes starts calling and chases after him until he relinquishes his catch. These “prey exchanges” are relatively frequent, especially while the chicks are still young. The female may then perch on a ledge and feast herself, or pluck the feathers off before bringing in some meat to the chicks.
Peregrine falcons are bird specialists. They are well-adapted to hunting other birds and almost never prey on rodents or other non-avian species. A hunting peregrine is an exhilarating spectacle! Although they have varied methods of hunting, oftentimes they will circle high in the air, then tuck their wings in and dive straight down upon their flying prey in what is called a “stoop.” While in these impressive stoops, they may achieve speeds of over 200 mph! The peregrine will then strike the other bird with its talons, stunning it and causing it to tumble in the air. The peregrine then grasps the falling bird with its talons and delivers a fatal bite to the neck vertebrae with its sharply curved beak.
Other interesting behaviors you may see if you stop in at the Precipice include the adults vigorously defending the area from other birds, especially large raptors. A juvenile bald eagle in the area likes to wander near the cliff. Although he is much larger than the peregrines, they don’t hesitate to dive at him and let him know he is not welcome! If low-flying turkey vultures come too close, even though they only eat carrion and are not a threat to the chicks, the adult peregrines send them on their way!
Because peregrine falcons are endangered in the state of Maine, we closely monitor the nest sites in the park and try to limit the amount of human disturbance at their nest sites. Therefore park staff close several trails: Precipice Trail, East Face Trail, the north section of Flying Mountain Trail (between the Valley Cove and Man of War Brook Fire Roads), and the Jordan Cliffs Trail. These trails will remain closed until it is determined that either the peregrine chicks are no longer using the cliff or the nest has failed—usually sometime in late July or early August. This helps to ensure that we continue to rebuild our peregrine population, which was essentially extirpated in the entire eastern U.S. in the 1960s.
Come join us at the Precipice parking lot for a look at these amazing raptors. The Precipice is staffed every day from 9 a.m. to 12 p.m., weather permitting.
- Lindsey Fenderson